DHAKA: A pro-Russian rebel leader in eastern Ukraine has said 3-4,000 Russian citizens are fighting in their ranks.

Alexander Zakharchenko told Russian TV many of the Russians were former servicepeople or current personnel on leave, reports the BBC.

He was speaking as rebels captured the town of Novoazovsk and threatened to take the city of Mariupol, after opening a new front in the south-east.

Reports say they are advancing on the city, a key port on the Sea of Azov.

Ukraine says Russian forces have crossed the border and are supporting the rebel attack, but Moscow has repeatedly denied arming or covertly supporting the rebels.

There are suspicions that Russia wants to divert Ukrainian forces from the besieged cities of Donetsk and Luhansk, further north.

Government forces have made significant advances against the separatists in recent weeks.

BDST: 1605 HRS, AUG 28, 2014